Production was reduced by 665 MW at the 900 MW Bugey 3, and by 300 MW at its 900 MW Fessenheim 2 reactor.

EDF said on Wednesday said that forecasts of high temperatures in the Rhone River could lead to the shutdown from Aug. 3 of four nuclear reactors which depend on its waters for cooling: Bugey 2 and 3, St Alban 1 and 2.

The utility discharges water it uses as coolant for the reactors into surrounding rivers and canals. The quantity and temperature of the water it discharges is regulated by law to protect plant and animal life, forcing EDF to cut output during prolonged hot weather when river temperatures rise.

On Friday, water temperature rose to over 26 degrees Celsius (78.8°F) upstream the Rhine River where Fessenheim is located. On the Rhone, the water temperature was also at 26 degrees, according to Thomson Reuters data.